Today, automobiles are equipped with various electric and electronic parts, electric circuits thereof are becoming more and more complicated. Thus, stable supply of power is indispensable. An automobile equipped with such various electric and electronic parts includes wire harnesses including insulated wires in a bundle. The wire harnesses are connected to each other by connectors to form an electric circuit.
Such a connector has a built-in crimp terminal for pressure-bonding and thus connecting an insulated wire thereto by a pressure-bonding section. A male connector and a female connector are in engagement with each other.
The electric circuit constructed by such electric connection has a problem that when moisture invades a pressure-bonded section at which the insulated wire is pressure-bonded to the crimp terminal located in the connector, a surface of the electric wire conductor included in the insulated wire is corroded and thus the conductivity thereof is decreased.
This problem is considered to occur for the following reason. There is a gap between an insulation barrel of the pressure-bonding section for pressure-bonding a tip part of a cover of the insulated wire and a wire barrel of the pressure-bonding section for pressure-bonding an exposed part of the electric wire conductor which is exposed from a tip of the cover. Therefore, the tip part of the cover is exposed.
It is considered that the invasion of the moisture can be prevented by integrally enclosing a part from the tip of the cover to the tip of the electric wire conductor by use of a crimp terminal (see Patent Document 1) including a barrel in which the wire barrel and the insulation barrel are integrated. However, recent electric circuits having a complicated structure need to have a more stable conductivity. Thus, the above-described crimp terminal is not sufficient.
Today, carbon dioxide emissions are required to be reduced, and electric automobiles and hybrid automobiles which use more wire harnesses than gasoline-fueled automobiles are used. In this situation, weight reduction of all types of vehicles including gas-fueled automobiles significantly influences improvement of fuel efficiency. Therefore, there is an attempt to reduce the weight of vehicles by using electric wires formed of aluminum (or aluminum alloy), as well as copper (or copper alloy), for wire harnesses, battery cables and the like.
When an aluminum wire formed of aluminum or an aluminum alloy is pressure-bonded to a crimp terminal formed of copper or a copper alloy, there is the following problem. If there is moisture such as dew condensation, seawater or the like at a contact part of the aluminum wire and the crimp terminal, an electrochemical reaction occurs. As a result, a phenomenon called “galvanic corrosion” occurs that aluminum or the aluminum alloy, which a metal material having a low potential, is corroded by a metal material having a high potential, such as tin plating, gold plating, copper alloy or the like, which is used as a terminal material.
Due to the galvanic corrosion, the aluminum wire pressure-bonded by the pressure-bonding section of the terminal is corroded, dissolved, or extinguished, which raises the electric resistance. As a result, a sufficient conducting function may not be provided. When such an aluminum wire is used, invasion of moisture needs to prevented with more certainty.
Patent Document 1 also describes applying an epoxy paint at the time of pressure-bonding for the purpose of improving a property of stopping moisture more certainly. However, application of a paint at the time of pressure-bonding is not preferable for mass production because additional time is needed for the step of application. It is also very difficult to apply a paint while the position and the amount of application are controlled with high precision at the time of pressure-bonding. For these reasons, the method of applying an epoxy paint at the time of pressure-bonding is not satisfactory.